The work of digital computers is controlled by applications programs, which govern the step-by-step operations performed by the computers in processing data. Verifying that a computer is processing the data in the manner desired by a programmer can be difficult to do, particularly if the program is required to be in any way complex. One way is for the programmer to verify that the logical flow of the program is as he or she intended by the studying the program. While this method may work for some gross errors, it may not be enough to facilitate discovery of all errors, particularly of errors that arise from, for example, errors or eccentricities in the way that the computer itself processes certain program instructions.
Debugger programs have been developed to facilitate debugging of other programs, termed here "applications programs," to ease the programmer's task of discovering and correcting the latter type of errors. Using a debugger program, a programmer can enable the particular computer for which the applications program is being written to process portions of the applications program, using known input data, to thereby enable the generation of output data. Since the input data is known, the programmer can determine what the output data should be, and compare the actual output data to that. If the actual output data corresponds to what the output data should be, the programmer can determine that the applications program is likely to be correct. On the other hand, if the actual output data does not correspond to what the output data should be, the programmer will know that further work is necessary to perfect the program.
In some cases, the amount of data generated by an application program, processed under control of a debugger program, can be quite voluminous. For example, many applications program operate on arrays of data, which arrays can be quite large and have many dimensions. Easy retrieval of portions of such arrays for display and examination using conventional debugger programs can be fairly difficult.